Effect of window layer composition in Cd1−xZnxS/CdTe solar cells

ABSTRACT To improve CdS/CdTe cell/module efficiencies, CdS window layer thinning is commonly applied despite the risk of increased pin‐hole defects and shunting. An alternative approach is to widen the band gap of the window layer (2.42 eV for CdS) via alloying, for example, by forming compositions of Cd1−xZnxS. In this study, the performance of Cd1−xZnxS/CdTe thin‐film solar cells has been studied as a function of x (from x = 0 to 0.9), widening the window layer band gap up to and over 3.4 eV. Optimum Cd1−xZnxS compositions were clearly identified to be around x = 0.7, and limitations to the achievable photocurrent and conversion efficiencies have been addressed. Copyright © 2012 John Wiley & Sons, Ltd. CdS window layer thinning is commonly applied to increase photocurrent in chalcogenide solar cells, despite the risk of increased shunting. An alternative approach, by forming compositions of Cd1−xZnxS, is shown to improve the blue response of CdTe solar cells. An optimum Zn content, found to be x ≈ 0.7, boosts the average conversion efficiency by 37%.